Ranging system



July 5, 1949. F. sLAYMAKER Erm. f 2,474,918 ,A

HANGING SYSTEM Filed July 50, 1945 2 sheets-sheet -2 HORN IVIC/(EL l I I I I I .l I I I I I l I l I I HTTOR/VFY Patented July 5, 1%49 RANGING SYSTEM Frank H. Slaymaker and Willard F. Meeker,

Rochester, N. Y., assignors to Stromberg-Carlson Company, Rochester, N. Y., a corporation of New York .Application July 30, 1945, Serial N0. .607,840

2 Claims. vl(Cl. 177-352) This invention relates to almethod of and tof apparatus for ranging andmore particularly to the location of unseen objects.

In many situations where it is not possible to' determine visuallythe location of objects, it is frequently desirable to provide'lwarning signals, preferably audible, whichtvary in characteristics, such as pitch, when -the observer approaches the objects or when the objects approach the ob-A server, as the case may be., 'In achieving this result it has been proposed in the past to employ a frequency modulation ranging system wherein a transmitter continuously'radiates signals varying in frequency such as according to a sawtooth pattern and wherein a receiver continuously receives the reflected signals or echoes. However, it has been discovered that Where continuous radiation and receptionuof `this type are employed, anomalies can occur which make the distance indication uncertain if not entirely erroneous in certain instances.

In accordance with the main feature of the present invention, there is provided a method and apparatus whereby reliable frequency modulation ranging may be elected.

Other features of the invention will appear from the detailed description and claims when taken with the drawings in which:

Fig. 1 is a chart useful in explaining the anomalies that can occur in conventional lranging systems;

Fig. 2 is a chart useful in explaining the novel method of the present invention;

Fig. 3 is a diagrammatic showing of the circuits and apparatus used in practicing the method of the present invention;

Fig.` 4 is a diagrammatic showing of a modified ranging system; and

Fig. 5 is a sectional view illustrating the construction of the magnetostriction device which can be used as a radiator or as a microphone.

In a frequency modulation ranging system Where there is a continuous radiation of a signal such as is indicated by the heavy saw-tooth 'curve 5, the echo of such a signal as it is reflected from distant objects or obstacles Will be of the same saw-tooth patternas the radiated signal but will be delayed in time. This may -be represented -by the dotted line saw-tooth curve 6 of Fig. 1. The difference in frequency between the radiated signal 5 and the echo 6 of that signal can be used to givel an indication of the distance from the radiator to the obstacle. This difference in frequency results in a beat lnote as indicated at 'l and 8 in Fig. As the distance from the radiator to the obstacle increases a portion of the beat note designated l increases in frequency while the portion of the beat note, designated 8, decreases in frequency. The presence of two beat notes changing in opposite directions with changes in distance can cause confusion.

` In accordance with the method of the present invention, it is proposed to eliminate one of the beat notes, such as By way of example, it is proposed to generate a single set of oscillations and to radiate a varying frequency signal during the rst part only of given periods. In effecting radiation, there is provided a local source of oscillations the frequency of which varies according to a saw-tooth pattern. The oscillator should continue to oscillate even during that portion of the period that the signal is not being radiated and the frequency should follow the original saw-tooth pattern. The method just referred to is indicated in the chart of Fig. 2 wherein the saw-tooth curve 9 represents the continuous Aoscillations the frequency of which varies periodically according to a given saw-tooth pattern. However, only that portion of frequencies 9 indicated by the heavy line 9a is radiated. The parts of the radiated signal which are reflected back as echoes, are indicated by the portions of the reflected saw-tooth curve indicated by the lines designated lll. The frequencies indicated by the lines lll combine with the oscillator frequencies il, to produce a beat note Il. From this chart it will be seen that the beat note between the echo and the oscillator frequencies becomes a series of short pulses, the frequency of each pulse being directly proportional to the distance from the radiator t-o the obstacle and back again to the point of reception.

While this method of ranging can be effected by various equipment, it is convenient to use the apparatus and circuits diagrammatically illustrated in Fig. 3. In this arrangement there is provided an oscillator I2 of the resistance-capacitance, phase-shift type. This oscillator, preferably, includes an electron discharge tube I3 of the pentode type comprising the cathode i4, control grid I5, screen grid l suppressor grid il and anode I8. The input circuit of the oscillator includes the cathode i4, in series with the biasing resistor I9 (which is oy-passed vby condenser Z). resistor 2i and control grid l5. The output of the oscillator tube including anode i8, is connected through a phase shift network to the control grid I5, in the well-known manner. This phase shift network ycomprises the condensers 22, 23 and 24 connected in series and the resistors 2|, 25 and 26 connected in multiple therewith. It will be understood that the oscillator frequency is determined in part by the values of the mentioned resistors and condensers. In the present arrangement, the plate resistances of vacuum tubes 28 and 29 designated "Variable resistance tubesg 'in Fig: 3, areirespectively.A con; nected in multiple with the resistors 25 andie'? and function as the adjustable part of the phase shift network by which the oscillator frequency is., controlled. The plate resistances of the control tubes 23 and 29 is a function of the potentialol'r-2 the grids 3D and 3| of these tubes r1:27111; potential on these grids in turn, follows ,the .v`ollt l'ge output of the saw-tooth osciltor '321. The? fre."- quency of the oscillator I2, therefore, varies in a saw-tooth manner. The output Ioiftljre.oscillha; tor lz is coupled through the eondeserswit i an output amplifier stage 35. As previously? mentioned, a portion only of the generated frequencies, namely band B (Fig. 2) is radiated. Inorder to limit theradiatedfrequencies tothe band B, a suitable band pass iiltendevice. bei coupled to the output; circuit of the output, amplierstage 35. In the presen-t arrangement* it is preferred that the band pass filter take the, form of aresonant:magnetostriction radiator 2B" which will` be described; TheY band of frequen., cies 9a (Fig. 2') will be radiated by radiator 35. andupony encountering theobject 31 will'be re"- iiected and pickedup bythe resonant magneto` striction microphone 38.- These reflected quencies will be amplified. in the high fre'qi'ie'nc'fyv amplifier 39` and ini the mixer'l tube 40 bel combined with oscillations from theoscillator; to developa beat note, such as IlA (Fig; 2i. This: beat note will be amplified in the audio ariplfi, fier 42 and can be heard in the headphones (3 1 As the distance between the object Bland nliciof..Y phone 33 changes, the pitch of the bea't note' willi change in a distinctive manner.

The resonant magnetostriction radiatorunit 36" and the resonant mag'rietos'i'iijic'tiorilv rnic'r'o phone unit 38, may be of the constructionV Inge'` fully disclosedin Fig. 5. This unit comprises" driver made up of theipolarizing.'` magnets; la'iii the-form of blocks mounted between the Ushaief, p'olepie'ce liliy and thefapertured nolep'ie'ee` IIT. Ai.' hollow' nickel tube 48 is secured at one.Y endl the' polepiece 46, so that its other end ei'te axially through the opening.y in the polepieceI IL The free endv of the nickel tube 48. has a' dia-l phragm U' secured thereto. A coil. Ml encircles. the tube' 38.v The unit also 4comprises a para# bolic hornk 5t, of wood orV like material, having"v an opening in itsl restrictedy end:` to receive-the diaphragm 5G. They driver unit and` the horn; are joinedV together with cushioning. material therebetweentending to -prevent mechanical coupling between the horn and the driver. 'lghe polarizing magnets 45 maintain a magnetic fieldE through the nickel tube 48. When a varying@ current flows through the coil 49, the field variesv andibecause of the magnetostipictive properties of nickel, the length ofthe nickel tubeAB, clfiarigefs,"A also. Since the back end of thenickel tube is fixed, the front end isf'free. to moyeand radiate sound. A suitable magnetostrictionftra u on is described and ,c laiineding a 1o-pend ygap cati-on of Frank. H. `Slayrnakerr,` Willard F-.. Mee if, and Lynn L. Merrill, Serial No;,67 6,42 5',1.e1.f1ue 1,;3, v1946,.and assignedto the saine;assignee.als'A thegpresent invention. y A g Since `the present invent/ion Inayzhayean'iifnff portant field of use in-.guiding-'the blind, the'lrang`f` '4 ing system can be made portable and the two magnetostriction units are mounted side by side on a common handle 52 (Figs. 3 and 4) so that they can be aimed by the user.

In the foregoing arrangement, the equivalent of a band pass filter was utilized to limit the radilated treqiniesto a. `b gmdf B, (Fig. 2v). but in meminciin i ibrfijg of inegiventjion mustraied in Fig. 4, the limitation of radiated frequencies i tg, band B is eiected by electronic switching nieansns in the arrangement of Fig. 3, the dssill'ato 60 is of the resistance-capacitance, pliaseshift type the unit 6| indudmg the y, T vari "eige is 'i1-bes (like those designated 1115"? Il 2.9; of controls the oscillator frequency. the saw-tooth oscillator 62 acting .pnntlie grids of the variable resistance teiifi'nnit Ul' causes the frequency of the oscil-ldtriij` to vary in a saw-tooth manner. The output of the oscillator 60 is delivered through alghilje tczagthe,oiitnut ampliiier stage incilygdin einer!" ,'rrieigrid s3 of the tubei il dut-'offvwith the g offestate will not 12 diatoral When Ba'r be radiated, p, t. lstage including 'red' conducting so Kthe'manner of an nt Lof. the voutput positive pulse to Q ubef to amplify. 'by' introducing a n oscillator into the E@ to develop 'an output inran'g'ernent of Fig.

en reflected signal'xs ctedain hesam mannera's in the arrarigernentw olf" 3T Cgingling receiving elements un.. Fi, 4v arel id tiadbygthe sam'e refnFig'.' 3` except for the principle of the invention has been sizeaallriselped .in...s .nnect0n with using supersonics' in air,i nir/fen ionis not so limited.

...ferr stimule Varianz; `e'ti1rir1suofthe Oscillating; .man .whereby there, era generated osillations; any all?" rammel to. frequency within-.fe meatballs! ,n acc rdanee withl asawt0n nattermmterinzi..

onli/'etsen finden@ tia-militie thesamemeans lvm saificeseiilatianswmn.renewed from is f-O ranslatinsfthere'- Il. os illations into, signals;

V'Sli continues tol 2. In a ranging system, oscillating means, means for cyclically varying the tuning of the REFERENCES CITED oscillating means whereby there are generated The following references are of record in the oscillations cyclically Varying as to frequency file 0f this patent: Within a given band accordance with a saw- 5 UNITED STATES PATENTS` tooth pattern, means including a resonant magnetostrictive unit for radiating oscillations of Number Name Date frequencies within a portion only of said band, 2,011,392 Bentley -1 Allg- 13, 1935 means including a resonant magnetostrictive unit 2,253,975 Guanella Aug. 26, 1941 of like characteristics as said rst mentioned unit l0 2,321,269 A117219 June 8, 1943 for receiving oscillations at frequencies within 2,371,933 GI'aIlqVSt Mar. 20, 1945 the mentioned portion of said band when reflected 2,405,134 BTOWII et 8,1- 1- Allg. 6, 1946 from objects, means for combining said received FOREIGN PATENTS oscillations with oscillations generated by said oscillating means, and means for translating the Number COU-@YY Date resultant of said combined oscillations into sig- 546302 Great Bntam July 2, 1942 nals.

FRANK H. SLAYMAKER. WILLARD F. MEEKER. 

